After the death of Alexander the Great in the afternoon of
11 June 323 BCE, his empire was divided by his generals,
the so-called
Diadochi. One of them was his friend Seleucus, who
became king of the eastern provinces - more or less modern
Afghanistan, Iran, Iraq, Syria, and Lebanon, together with
parts of Turkey, Armenia, Turkmenistan, Uzbekistan, and
Tajikistan. His kingdom had two capitals, which he founded
in c.300: Antioch in Syria (pictures) and Seleucia in
Iraq. Babylon was a third important city. The empire was,
like the empire of Alexander, actually the continuation of
the empires before: Persia, Babylonia and Assyria.

Seleucus I

Seleucus' reign lasted from 312 to 280 , and he was
succeeded by his descendants, who continued to govern
these countries for two centuries. But c.246, during a
short interregnum, the Seleucids lost much territory in
the east, where the
Parni settled themselves in the satrapy of
Parthia -in northern Iran- and the satrapy of Bactria
-Afghanistan- became independent. The Seleucid king
Antiochus III the Great was able to reconquer these
territories between 209 and 204. In the southwest, the
Seleucid kings fought several wars with the Egyptians; in
200, their king was forced to cede Palestine to Antiochus
III. Seleucid power was at its zenith.

Antiochus III
the Great

In 196, Antiochus III crossed the Hellespont in order to
add Thrace to his empire (which happened in 194). This was
something that the Romans could not allow to happen, and
war between the two superpowers broke out in 192.
Antiochus received support from many Greek towns and help
from the famous general Hannibal, but was defeated and
forced to pay a tremendous sum of money. Moreover, the
Seleucid empire lost its possessions in what is now
Turkey.

Pompey the Great

The tide was turning against the Seleucid monarchy. In the
west, Rome became too powerful to resist; they backed the
Jews, who liberated themselves in the years after 165 (the
so-called Maccabaean revolt). At the same time, the Parni
founded the Parthian empire, which seized away the eastern
provinces. The towns in Babylonia, a.o. Seleucia and
Babylon, were captured between April and June 141. New
losses followed, until in 64, the Roman general Pompey the
Great made an end to the Seleucid kingdom.